According to the American Heart Association nearly 383,000 out-of-hospital sudden cardiac arrests occur annually in the United States. These patients may be saved by the timely application of life saving measures such as Cardiopulmonary resuscitation (CPR).
CPR is a well-known and valuable method of first aid used to resuscitate people who have suffered from cardiac arrest. CPR requires repetitive chest compressions to squeeze the heart and the thoracic cavity to pump blood through the body. Artificial respiration, such as mouth-to-mouth breathing or a bag mask device, is used to supply air to the lungs. When a first aid provider performs manual chest compression effectively, blood flow in the body is about 25% to 30% of normal blood flow. However, even experienced paramedics cannot maintain adequate chest compressions for more than a few minutes. Hightower, et al., Decay In Quality Of Chest Compressions Over Time, 26 Ann. Emerg. Med. 300 (September 1995). Thus, CPR is not often successful at sustaining or reviving the patient. Nevertheless, if chest compressions could be adequately maintained, then cardiac arrest victims could be sustained for extended periods of time. Occasional reports of extended chest compression efforts (45 to 90 minutes) have been reported, with the victims eventually being saved by coronary bypass surgery. See Tovar, et al., Successful Myocardial Revascularization and Neurologic Recovery, 22 Texas Heart J. 271 (1995).
In efforts to provide better blood flow and increase the effectiveness of bystander resuscitation efforts, various mechanical devices have been proposed for performing AUTOMATED CHEST COMPRESSIONS. In one variation of such devices, a belt is placed around the patient's chest and the belt is used to effect chest compressions. Our own patents, Mollenauer, et al., Resuscitation Device having a Motor Driven Belt to Constrict/Compress the Chest, U.S. Pat. No. 6,142,962 (Nov. 7, 2000); Sherman, et al., CPR Assist Device with Pressure Bladder Feedback, U.S. Pat. No. 6,616,620 (Sep. 9, 2003); Sherman, et al., Modular CPR Assist Device, U.S. Pat. No. 6,066,106 (May 23, 2000); and Sherman, et al., Modular CPR Assist Device, U.S. Pat. No. 6,398,745 (Jun. 4, 2002), and our application Ser. No. 09/866,377 filed on May 25, 2001, show chest compression devices that compress a patient's chest with a belt. Various other mechanisms may be used to tighten the belt, including the mechanisms shown in Lach, et al., Resuscitation Method and Device, U.S. Pat. No. 4,774,160 (Sep. 13, 1988) and in Kelly, et al., Chest Compression Device for Cardiac Arrest, U.S. Pat. No. 5,738,637 (Apr. 14, 1998).
Piston based chest compression systems are illustrated in Nilsson, et al., CPR Device and Method, U.S. Patent Publication 2010/0185127 (Jul. 22, 2010), Sebelius, et al., Support Structure, U.S. Patent Publication 2009/0260637 (Oct. 22, 2009), Sebelius, et al., Rigid Support Structure on Two Legs for CPR, U.S. Pat. No. 7,569,021 (Aug. 4, 2009), Steen, Systems and Procedures for Treating Cardiac Arrest, U.S. Pat. No. 7,226,427 (Jun. 5, 2007) and King, Gas-Driven Chest Compression Device, U.S. Patent Publication 2010/0004572 (Jan. 7, 2010) all of which are hereby incorporated by reference.
As mechanical compressions are performed by piston based chest compression systems, the compression pads may shift position relative to the patient and the effectiveness of the automated chest compressions are diminished. The repeated extension and retraction of the piston often results in the piston and compression cup moving or “walking” up the patient's chest toward the neck or moving down toward the patient's abdomen.